U.S. patent application number 12/888819 was filed with the patent office on 2011-03-24 for endoscope apparatus and illumination control method of endoscope apparatus.
This patent application is currently assigned to FUJIFILM Corporation. Invention is credited to Takayuki IIda, Satoshi OZAWA.
Application Number | 20110069163 12/888819 |
Document ID | / |
Family ID | 43382528 |
Filed Date | 2011-03-24 |
United States Patent
Application |
20110069163 |
Kind Code |
A1 |
OZAWA; Satoshi ; et
al. |
March 24, 2011 |
ENDOSCOPE APPARATUS AND ILLUMINATION CONTROL METHOD OF ENDOSCOPE
APPARATUS
Abstract
Provided are a plurality of semiconductor light emitting
elements having different central light emission wavelengths, a
multiplexer means for multiplexing lights, and a central wavelength
converting means for controlling a light emission amount ratio of
the plurality of semiconductor light emitting elements by the use
of a wavelength conversion table in which a central wavelength of
multiplexed laser light is obtained on the basis of information of
a light emission amount and the central light emission wavelengths.
Accordingly, the central wavelength of the multiplexed light is
controlled to be a predetermined wavelength.
Inventors: |
OZAWA; Satoshi; (Kanagawa,
JP) ; IIda; Takayuki; (Kanagawa, JP) |
Assignee: |
FUJIFILM Corporation
Tokyo
JP
|
Family ID: |
43382528 |
Appl. No.: |
12/888819 |
Filed: |
September 23, 2010 |
Current U.S.
Class: |
348/68 ;
348/E7.085 |
Current CPC
Class: |
A61B 1/0653 20130101;
H05B 45/22 20200101; A61B 1/0638 20130101; A61B 1/063 20130101 |
Class at
Publication: |
348/68 ;
348/E07.085 |
International
Class: |
H04N 7/18 20060101
H04N007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2009 |
JP |
P2009-219246 |
Claims
1. An endoscope apparatus including: an endoscope that includes an
illumination optical system having at least one of a plurality of
fluorescent substance; and a light source unit that is connected to
the endoscope, includes a plurality of semiconductor light emitting
elements having different central light emission wavelengths, and
supplies light from the semiconductor light emitting elements to
the illumination optical system; the endoscope system comprising: a
multiplexer unit that multiplexes the lights output from the
plurality of semiconductor light emitting elements; and a central
wavelength converting unit that controls a light emission amount
ratio of the plurality of semiconductor light emitting elements and
converts the central wavelength of the light multiplexed by the
multiplexer unit.
2. The endoscope apparatus according to claim 1, wherein the
central wavelength converting unit has a wavelength conversion
table in which the central wavelength of the light formed by
multiplexing the lights emitted from the plurality of semiconductor
light emitting elements is obtained on the basis of information of
the light emission amounts and the central light emission
wavelengths of the plurality of semiconductor light emitting
elements, and the light emission amount ratio of the semiconductor
light emitting elements is determined by referring to the
wavelength conversion table.
3. The endoscope apparatus according to claim 1, further
comprising: a demultiplexer unit that demultiplexes the multiplexed
light output from the multiplexer unit; wherein the plurality of
the fluorescent substances is disposed at different positions of an
endoscope front end portion to be inserted into a test object, and
the demultiplexer unit supplies the demultiplexed light to each of
the plurality of fluorescent substances.
4. The endoscope apparatus according to claim 1, further
comprising: an output light extracting unit that individually
extracts the lights output from the plurality of semiconductor
light emitting elements in a course of an optical path; and a
wavelength measurement unit that measures a wavelength of each of
the lights extracted by the output light extracting unit, wherein
the central wavelength converting unit determines the light
emission amount ratio on the basis of the wavelength measurement
values of the lights emitted from the plurality of semiconductor
light emitting elements.
5. An illumination control method of an endoscope apparatus
including an endoscope that includes an illumination optical system
having a fluorescent substance; and a light source unit that is
connected to the endoscope, includes a plurality of semiconductor
light emitting elements having different central light emission
wavelengths, and supplies light from the semiconductor light
emitting elements to the illumination optical system, the method
comprising at least the steps of: measuring the central light
emission wavelength of each of the semiconductor light emitting
elements; obtaining a central wavelength of light formed by
multiplexing the lights emitted from the plurality of semiconductor
light emitting elements through analysis in accordance with setting
values of the central light emission wavelength of each of the
semiconductor light emitting elements and a light emission amount
of each of the semiconductor light emitting elements, and
registering the central wavelength in a wavelength conversion
table; determining a light emission amount ratio of the
semiconductor light emitting elements so that the central
wavelength of the multiplexed light is equal to a target wavelength
on the basis of the wavelength conversion table; and driving the
semiconductor light emitting elements in accordance with the
determined light emission amount ratio.
Description
[0001] The present application claims priority from Japanese Patent
Application No. 2009-219246 filed on Sep. 24, 2009, the entire
content of which is incorporated herein by reference.
BACKGROUND OF INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an endoscope apparatus and
an illumination control method of the endoscope apparatus.
[0004] 2. Description of the Related Art
[0005] For example, JP-A-2006-296656 discloses an endoscope
apparatus including an illumination means for emitting laser light
from a semiconductor light emitting element to a fluorescent
substance so as to perform white illumination by exciting the
fluorescent substance to emit light. According to this kind of
endoscope apparatus, by using the laser light, it is possible to
obtain high illumination light which has lower power consumption
than that of a halogen lamp or xenon lamp. However, in the
semiconductor light emitting element, even in a product having the
same specification, there is differences in the light emission
wavelength in accordance with the conditions of the manufacturing
process or the materials to be used. Due to differences in the
light emission wavelength, the light emission efficiency of the
fluorescent substance may be reduced even by a slight difference in
the wavelength in accordance with the material of the fluorescent
substance. In this case, since the energy applied to the
semiconductor light emitting element needs to be increased in order
to obtain a predetermined light amount, needless energy loss
occurs.
[0006] Particularly, in the case where the absorption spectrum of
the fluorescent substance in a blue wavelength bandwidth is a rapid
profile, the light emission efficiency of the fluorescent substance
is increased or decreased due to a slight variation in the light
emission wavelength of the semiconductor light emitting element. As
a result, even when the fluorescent substance is illuminated by the
same light emission intensity, the light emission intensity of the
fluorescent substance is reduced, and hence bluish-white
illumination is performed. Likewise, due to differences in the
light emission wavelength, a difference occurs in the light
emission spectrum of the white light formed by the laser light and
the excitation light, and variations occur in the tone of the
image, thereby causing a problem in that a correct diagnosis may be
impeded.
[0007] In addition, the spectral sensitivity of the imaging element
may be easily and largely deteriorated around 400 nm. In the case
of using the semiconductor light emitting element having a short
wavelength substantially equal to 400 nm, a slight difference in
the light emission wavelength influences the light receiving
sensitivity of the imaging element. For this reason, the wavelength
of the light emitted from the semiconductor light emitting element
needs to be maintained with high precision to be a stipulated
constant value.
[0008] Further, in the manufacturing process of the semiconductor
light emitting element, a product inspection step is performed
after manufacturing so as to remove through inspection products
which are out of the stipulated light emission wavelength range,
and only products having similar quality levels are supplied to the
market. Accordingly, the cost of the components of the
semiconductor light emitting element tends to easily increase,
which impedes a decrease in the cost of the endoscope
apparatus.
SUMMARY OF INVENTION
[0009] An object of the present invention is to prevent
deterioration in the illumination light amount or imaging
sensitivity and to reduce the cost of components of an endoscope
apparatus. The endoscope apparatus and its illumination control
method are capable of highly precisely maintaining a wavelength of
light emitted from a semiconductor light emitting element at a
stipulated constant value and generating laser light of a
stipulated wavelength even with a single semiconductor light
emitting element the light emission wavelength of which is not
included in a stipulated wavelength range.
[0010] The present invention has the following configuration.
[0011] (1) An endoscope apparatus including: an endoscope which
includes an illumination optical system having a fluorescent
substance; a light source unit which is connected to the endoscope,
includes a plurality of semiconductor light emitting elements
having different central light emission wavelengths, and supplies
light from the semiconductor light emitting elements to the
illumination optical system; a multiplexer means for multiplexing
the lights output from the plurality of semiconductor light
emitting elements; and a central wavelength converting means for
controlling the light emission amount ratio of the plurality of
semiconductor light emitting elements and converting the central
wavelength of the light multiplexed by the multiplexer means.
[0012] (2) An illumination control method of an endoscope apparatus
including an endoscope which includes an illumination optical
system having a fluorescent substance; and a light source unit
which is connected to the endoscope, includes a plurality of
semiconductor light emitting elements having different central
light emission wavelengths, and supplies light from the
semiconductor light emitting elements to the illumination optical
system, the illumination control method including at least the
steps of: measuring the central light emission wavelength of each
of the semiconductor light emitting elements; obtaining a central
wavelength of light formed by multiplexing the lights output from
the plurality of semiconductor light emitting elements in
accordance with setting values of the central light emission
wavelength of each of the semiconductor light emitting elements and
a light emission amount of each of the semiconductor light emitting
elements, and registering the central wavelength in a wavelength
conversion table; determining the light emission amount ratio of
the semiconductor light emitting elements so that the central
wavelength of the multiplexed light is equal to a target wavelength
on the basis of the wavelength conversion table; and driving the
semiconductor light emitting elements in accordance with the
determined light emission amount ratio.
[0013] According to the endoscope apparatus and the illumination
control method of the endoscope apparatus of the present invention,
it is possible to highly precisely maintain the wavelength of the
light emitted from the semiconductor light emitting element to be a
stipulated constant value. In addition, even in the single
semiconductor light emitting element having the light emission
wavelength not included in the stipulated wavelength range, it is
possible to generate the light of the stipulated wavelength in such
a manner that the light emission amount ratio is controlled by the
combination of the plurality of semiconductor light emitting
elements. Accordingly, it is possible to prevent deterioration of
the illumination light amount or imaging sensitivity, and to reduce
the cost of components of the endoscope apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a diagram illustrating an embodiment of the
present invention, and is a conceptual block diagram of an
endoscope apparatus;
[0015] FIG. 2 is an external view as an example of the endoscope
apparatus shown in FIG. 1;
[0016] FIG. 3 is a graph showing a light emission spectrum of a
blue laser light generated from a blue laser light source and a
light emission spectrum in which the wavelength of the blue laser
light is converted by a fluorescent substance;
[0017] FIG. 4 is a graph showing an example of an excitation
spectrum and an emission spectrum of a fluorescent substance;
[0018] FIG. 5 is an explanatory diagram showing that the light
emission intensity of a fluorescent substance is changed in
accordance with the magnitude of absorbed energy;
[0019] FIGS. 6A to 6D are graphs showing spectrums of synthetic
laser lights formed by multiplexing two laser lights having
different light emission wavelengths and light emission intensities
in accordance with predetermined light amount ratios;
[0020] FIG. 7 is a graph showing a relationship between the light
amount ratio and the central wavelength of synthetic laser light
when light emission wavelengths of two laser lights having
different wavelengths are set to be uniform;
[0021] FIG. 8 is a flowchart showing a procedure of obtaining
synthetic laser light having a desired wavelength by multiplexing
two laser lights having different light emission intensities;
[0022] FIG. 9 is a conceptual block diagram of the endoscope
apparatus of a modified example 1;
[0023] FIG. 10 is a block diagram showing a configuration of a main
part of a light source device of a modified example 2; and
[0024] FIG. 11 is a block diagram showing a configuration of a main
part of a light source device of a modified example 3.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0025] Hereinafter, an embodiment of the invention will be
described with reference to the accompanying drawings.
[0026] FIG. 1 is a diagram illustrating an embodiment of the
invention, and is a conceptual block diagram of an endoscope
apparatus. FIG. 2 is an external view of an example of the
endoscope apparatus shown in FIG. 1.
[0027] As shown in FIGS. 1 and 2, an endoscope apparatus 100
includes an endoscope 11, and a control device 13 to which the
endoscope 11 is connected. The control device 13 is connected to a
display unit 15 which displays image information or the like, and
an input unit 17 which receives an input operation. The endoscope
11 is an electronic endoscope which includes an illumination
optical system emitting an illumination light from a front end of
an endoscope insertion unit 19 and an imaging optical system
including an imaging element 21 (refer to FIG. 1) configured to
image an observation area.
[0028] In addition, the endoscope 11 includes the endoscope
insertion unit 19 which is inserted into a test object, an
operation unit 23 (refer to FIG. 2) which is used for an operation
of curving the front end of the endoscope insertion unit 19 or an
observation operation, and connectors 25A and 25B which are used to
attachably/detachably connect the endoscope 11 to the control
device 13. In addition, although not shown in the drawings, the
inside of the operation unit 23 and the endoscope insertion unit 19
is provided with various channels such as a clamp channel used for
inserting a tissue pickup treatment tool or the like therethrough
or an air/water feeding channel.
[0029] The endoscope insertion unit 19 includes a flexible portion
31 which has flexibility, a curved portion 33, and a front end
portion (hereinafter, referred to as an endoscope front end
portion) 35. As shown in FIG. 1, the endoscope front end portion 35
is provided with illumination ports 37A and 37B which are used to
emit a light to the observation area, and an imaging sensor 21 such
as a CCD (Charge Coupled Device) image sensor or a CMOS
(Complementary Metal-Oxide Semiconductor) image sensor which is
used to acquire image information of the observation area. The
light receiving surface of the imaging element 21 is provided with
an object lens unit 39.
[0030] The curved portion 33 is provided between the flexible
portion 31 and the front end portion 35, and is adapted to be
curved by a rotation operation of an angle knob 22 disposed in the
operation unit 23. The curved portion 33 may be curved to an
arbitrary direction and an arbitrary angle in accordance with a
portion of the test object examined by the endoscope 11. The
observation direction of the illumination ports 37A and 37B and the
imaging element 21 of the endoscope front end portion 35 may be
directed to a desired observation portion. In addition, the
illumination ports 37A and 37B of the endoscope insertion unit 19
are provided with a cover glass or a lens (not shown).
[0031] The control device 13 includes a light source device 41
which generates an illumination light supplied to the illumination
ports 37A and 37B of the endoscope front end portion 35, and a
processor 43 which performs an image process on an image signal
generated from the imaging element 21, and is connected to the
endoscope 11 via the connectors 25A and 25B. In addition, the
processor 43 is connected to the display unit 15 and the input unit
17 which are described above. The processor 43 performs an image
process on an imaging signal transmitted from the endoscope 11 on
the basis of the command from the operation unit 23 of the
endoscope 11 or the input unit 17 thereof, and generates and
supplies a display image to the display unit 15.
[0032] The light source device 41 includes two blue laser light
sources 45 and 47 which generate a blue laser light in which the
central wavelength is stipulated as about 445 nm. In these blue
laser light sources 45 and 47, for example, a semiconductor light
emitting element LD1 having a central wavelength of 444 nm is
provided as a light emission source of the blue laser light source
45, and a semiconductor light emitting element LD2 having a central
wavelength of 446 nm is provided as a light emission source of the
blue laser light source 47. In addition, each of the semiconductor
light emitting elements LD1 and LD2 is individually controlled by a
light source control section 49, and the light amount ratio between
the light emitted from the blue laser light source 45 and the light
emitted from the blue laser light source 47 is individually
changeable.
[0033] The semiconductor light emitting elements LD1 and LD2 may
use an InGaN-based laser diode of a broad area type, and also may
use an InGaNAs-based laser diode or a GaNAs-based laser diode. In
addition, as the above-described light source, a light emitting
member such as a light emitting diode may be used.
[0034] In the blue laser lights emitted from the blue laser light
sources 45 and 47, each of the emission wavelengths is measured in
advance, and the emission wavelength is stored in a storage section
75 connected to the light source control section 49.
[0035] The blue laser lights emitted from the light sources 45 and
47 are respectively input to optical fibers 55A and 55B by a
condensing lens (not shown), and are propagated to the connector
25A via a combiner 51 as a multiplexer and a coupler 53 as a
demultiplexer. In addition, the invention is not limited thereto,
but has a configuration in which the laser lights emitted from the
light sources 45 and 47 are directly supplied to the connector 25A
without using the combiner 51 and the coupler 53.
[0036] The blue laser light obtained by multiplexing two blue laser
lights having a central wavelength of 445 nm is propagated to the
connector 25A, and is propagated to the endoscope front end portion
35 of the endoscope 11 by the optical fibers 55A and 55B. Then, the
blue laser light excites a fluorescent substance 57, which is a
wavelength converting member disposed in the light emitting ends of
the optical fibers 55A and 55B of the endoscope front end portion
35, so as to emit light therefrom. Further, a part of the blue
laser light directly passes through the fluorescent substance
57.
[0037] The fluorescent substance 57 includes plural types of
fluorescent substances (for example, a YAG-based fluorescent
substance or a fluorescent substance such as
BAM(BaMgAl.sub.10O.sub.17)) which absorbs a part of the blue laser
light and is excited to emit light as green to yellow. Accordingly,
the blue laser light is changed to white (color similar to white)
illumination light by mixing green to yellow excitation light as
the excitation light with the blue laser light not absorbed and
transmitted by the fluorescent substance 57. Like the example of
the configuration, when the semiconductor light emitting elements
LD1 and LD2 are used as an excitation light source, it is possible
to obtain a white light having a high emission efficiency and a
high intensity. Also, it is possible to easily control the
intensity of the white light, and to minimally suppress variation
in the color temperature and chromaticity of the white light.
[0038] The fluorescent substance 57 may prevent an occurrence of
flickering when performing a video display or overlapping of noise
as a barrier in the imaging operation due to a speckle generated by
coherence of laser light. In addition, in the fluorescent substance
57, in consideration of differences in the refractive index between
the fluorescent material forming the fluorescent substance and a
fixing/solidifying resin as a filling agent, it is desirable that
the particles of the filling agents and the fluorescent material
are formed of a material having large scattering and small
absorption with respect to the infrared light. Accordingly, it is
possible to improve the scattering effect without reducing the
light intensity with respect to the light of red or infrared
region, and to reduce the optical loss.
[0039] The optical fibers 55A and 55B are multi-mode fibers. As an
example, a thin fiber cable may be used which has a core diameter
of 105 .mu.m, a cladding diameter of 125 .mu.m, and a diameter of
00.3 to 0.5 mm including a protection layer as an outer
surface.
[0040] FIG. 3 is a graph showing a light emission spectrum of a
blue laser light generated from a blue laser light source and a
light emission spectrum in which the wavelength of the blue laser
light is converted by a fluorescent substance. The blue laser light
is depicted by the bright line having a central wavelength of 445
nm, and the excitation light emitted from the fluorescent substance
57 by the blue laser light has a spectral intensity distribution in
which the light emission intensity substantially increases in the
bandwidth of the wavelength of 450 nm to 700 nm. The
above-described white light is formed by the profile of the
excitation light and the blue laser light.
[0041] Accordingly, the white light mentioned in the specification
precisely includes not only all the wavelength components of
visible light, but also for example, R, G, B, and the like of light
of a specific wavelength. For example, light including a wavelength
component from green to red or the light including the wavelength
component from blue to green is in a broad sense included in the
white light.
[0042] In the endoscope apparatus 100, the emission intensity of
the profile shown in FIG. 3 is controlled to be increased and
decreased by the light source control section 49, thereby
generating illumination light having arbitrary luminance
balance.
[0043] Here, the profile shown in FIG. 3 will be described in more
detail with reference to FIGS. 4 and 5.
[0044] FIG. 4 is a graph showing an example of an excitation
spectrum and a light emission spectrum of a fluorescent substance.
In the fluorescent substance of this case, the excitation spectrum
indicated by the dotted line is allowed to absorb the light in the
bandwidth of the wavelength of about 420 to 470 nm, and
particularly to absorb the light of the wavelength of about 445 nm
with high efficiency. The fluorescent substance 57 is excited by
the absorbed excitation light, and emits fluorescence of the
spectrum depicted by the light emission spectrum indicated by the
solid line.
[0045] The light emission intensity of the fluorescent substance 57
is changed in accordance with the magnitude of the absorbed energy.
For example, as shown in FIG. 5, if it is assumed that the light
emission wavelength of the blue laser light source is deviated, in
the laser beam LB-A of the stipulated wavelength of 445 nm, highly
efficient absorption occurs at a wavelength at which the excitation
spectrum substantially reaches the peak. However, in the laser beam
of LB-B, since the light emission wavelength is deviated, the
intensity of the excitation spectrum is decreased by .DELTA.P.
Then, in the laser beam LB-B, the light intensity is the same as
that of the laser beam LB-A, and the light emission spectrum of the
fluorescent substance is decreased from CA to CB, which causes a
relative difference in the light emission intensity of the
fluorescent substance.
[0046] Then, in the white light formed by the light emission of the
fluorescent substance and the blue laser light, the tone of the
white light is changed due to a variation in the intensity balance
of the light emission (a variation in accordance with the
wavelength) of the fluorescent substance and the blue laser light
(uniform intensity). That is, in the case where the light emission
wavelength is deviated as in the laser beam LB-B, the light
emission intensity of the fluorescent substance is decreased, and
the intensity ratio of the blue laser light is relatively
increased, which makes the bluish-white light.
[0047] Likewise, in order to make the tone of the illumination
light uniform, it is necessary to make the wavelength of the laser
light source uniform with high precision. For this reason, in the
endoscope apparatus with such a configuration, a plurality of laser
light sources is used, and the respective laser lights are
multiplexed, thereby reducing the influence caused by individual
differences of the wavelengths of the emission lights included in
the laser light sources. By multiplexing the laser lights output
from the plurality of laser light sources, it is possible to set
the central wavelength of the multiplexed laser light to the
average wavelength of the respective laser light sources, that is,
the wavelength substantially equal to the stipulated wavelength
(445 nm)
[0048] Returning to FIG. 1, the description thereof is continued.
As described above, the white illumination light formed by the
excitation light emitted from the fluorescent substance 57 and the
blue laser light is emitted from the front end portion 35 of the
endoscope 11 to the observation area of the test object. Then, the
image of the observation area illuminated by the illumination light
is formed on the light receiving surface of the imaging element 21
by the use of the object lens unit 39.
[0049] The image signal of the captured image output from the
imaging element 21 after the imaging operation thereof is
transmitted to an A/D converter 65 via a scope cable 63 and is
converted into a digital signal. Then, the digital signal is input
to an image processing section 67 of the processor 43 via the
connector 25B. The image processing section 67 converts the input
digital image signal into image data. The converted image data is
appropriately subjected to an image process by the image processing
section 67, and is output to a desired output image information
control section 73.
[0050] The output image information input to the control section 73
is displayed as an endoscope observation image in the display unit
15, and is stored in the storage section 75 including a memory or a
storage device, if necessary.
[0051] Next, the multiplexing operation of the laser lights emitted
from two blue laser light sources 45 and 47 having slightly
different light emission wavelengths will be described.
[0052] FIGS. 6A to 6D show a spectrum of a synthetic laser light
obtained by multiplexing two laser lights having different light
emission wavelengths and light emission intensities.
[0053] As shown in FIG. 6A, the synthetic laser light LBC of the
spectrum depicted by the solid line may be obtained by multiplexing
the blue laser light LB1 having the central light emission
wavelength .lamda..sub.LD2 emitted from one blue laser light source
47 depicted by the one-dotted dashed line and the blue laser light
LB2 having the central light emission wavelength .lamda..sub.LD1
emitted from the other blue laser light source 45 depicted by the
two-dotted dashed line and having the central wavelength shorter
than that of the blue laser light LB1. In addition, each of the
light emission wavelengths .lamda..sub.LD1 and .lamda..sub.LD2 of
two blue laser lights LB1 and LB2 emitted from the blue laser light
sources 45 and 47 is a uniform wavelength. In addition, in FIGS. 6A
to 6D, for easy comparison with the light emission wavelengths of
the blue laser lights LB1 and LB2, the scale of the light emission
intensity of the synthetic laser light LBC is depicted to be
1/2.
[0054] FIG. 6A shows the spectrum of the synthetic laser light LBC
when the blue laser lights LB1 and LB2 having the same light amount
ratio (LD1:LD2=1:1) are emitted from the blue laser light sources
45 and 47. At this time, the central wavelength .lamda.a of the
synthetic laser light LBC is a middle value between the central
wavelengths .lamda..sub.LD1 and .lamda..sub.LD2 of the blue laser
lights LB1 and LB2.
[0055] FIG. 6B shows the spectrum in the case where the lights are
respectively emitted from the blue laser light sources 45 and 47 so
as to have a different light amount ratio therebetween, and the
light amount ratio is set to LD1:LD2=1.3:1. At this time, the
central wavelength .lamda.b of the synthetic laser light LBC is
shifted to the central wavelength .lamda..sub.LD1 of the blue laser
light LB1 having strong intensity from the middle value between the
central wavelengths .lamda..sub.LD1 and .lamda..sub.LD2 of the blue
laser lights LB1 and LB2.
[0056] Also, FIG. 6C shows the spectrum in the case where the
lights are respectively emitted from the blue laser light sources
45 and 47 so as to have a light amount ratio of LD1:LD2=1.5:1. FIG.
6D shows the spectrum in the case where the lights are respectively
emitted from the blue laser light sources 45 and 47 so as to have a
light amount ratio of LD1:LD2=2.0:1. Here, the central wavelengths
of the synthetic laser lights LBC are .lamda.c and .lamda.d, and
are further shifted to the central wavelength .lamda..sub.LD1 of
the blue laser light LB1.
[0057] FIG. 7 is a graph showing a relationship between the light
amount ratio of the blue laser lights LB1 and LB2 having the
central wavelengths .lamda..sub.LD1 and .lamda..sub.LD2 emitted
from the blue laser light sources 45 and 47 and the central
wavelength of the synthetic laser light LBC. When light emission
wavelengths .lamda..sub.LD1 and .lamda..sub.LD2 of the blue laser
light sources 45 and 47 are respectively set to be uniform, the
central wavelength of the synthetic laser light LDC is shifted to
the wavelength in which the intensity is increased. In other words,
when the light amount ratio of the respective blue laser lights is
controlled, it is possible to set the central wavelength of the
synthetic laser light to an arbitrary wavelength between the light
emission wavelengths of the respective blue laser lights.
[0058] Next, a driving procedure of the blue laser light sources 45
and 47 (LD1 and LD2) for adjusting the wavelength of the synthetic
laser light to be a desired wavelength in the endoscope apparatus
100 will be described in detail with reference to the flowchart of
FIG. 8.
[0059] First, the central wavelengths .lamda..sub.LD1 and
.lamda..sub.LD2 emitted from two semiconductor light emitting
elements LD1 and LD2 are respectively measured by a wavelength
measurement device (Step S1). Then, the central wavelength of the
synthetic laser light when changing the light emission amount of
each of the LD1 and LD2 is obtained through analysis from the
measured central wavelengths, a wavelength conversion table showing
a relationship between the light amount ratio of the LD1 and LD2
and the wavelength of the synthetic laser light is created, and
then the wavelength conversion table is stored in the storage
section 75 shown in FIG. 1 (Step S2). It is desirable that the
operations in Steps S1 and S2 are performed during the
manufacturing process of the endoscope apparatus 100, that is, the
time until the shipment of the product.
[0060] Then, when a switch 79 (refer to FIG. 1) disposed in the
operation unit 23 is operated during the usage of the endoscope
apparatus 100, this operation is considered as a calibration start
point. Accordingly, the light source control section 49 obtains the
light amount ratio of the laser lights to be emitted from the light
sources LD1 and LD2 so that the central wavelength of the synthetic
laser light is equal to the target wavelength by referring to the
wavelength conversion table registered in the storage section 75
(Step S3), and drives the light sources LD1 and LD2 in accordance
with the light amount ratio (Step S4). Accordingly, the central
wavelength of the synthetic laser light is controlled to be equal
to the arbitrary wavelength as the target. The target wavelength is
basically set as an original value in the endoscope apparatus 100.
However, for example, the target wavelength may be set in
accordance with the type of the endoscope 11 connected to the
control device 13 shown in FIG. 1, or may be set to an arbitrary
value which is input from the outside.
[0061] Incidentally, the semiconductor light emitting elements LD1
and LD2 used as the light emission sources of the blue laser light
sources 45 and 47 are divided into groups in accordance with the
light emission wavelength through a product inspection step in the
manufacturing process. For example, there are divided groups such
that one standard group equal to or more than 444 nm and less than
446 nm includes the central wavelength of 445 nm, and the other
group is not included in the range. Generally, only the
semiconductor light emitting elements LD1 and LD2 of the standard
group are used while being mounted to the light source device 41,
and the semiconductor light emitting elements LD1 and LD2 of the
other group (out of the standard group) are not used in this kind
of light source device 41. However, according to the endoscope
apparatus 100 with such a configuration, even the semiconductor
light emitting elements LD1 and LD2 out of the standard group may
be actively used as the illumination light source.
[0062] That is, in the case where the semiconductor light emitting
elements LD1 and LD2 out of the standard group are divided into a
first short wavelength group equal to or more than 440 nm and less
than 444 nm and a second long wavelength group equal to or more
than 446 nm and less than 449 nm, the semiconductor light emitting
elements LD1 and LD2 are respectively extracted from the first
group and the second group, and are used as the light emission
sources of the above-described blue laser light sources 45 and
47.
[0063] In other words, a pair of the semiconductor light emitting
element LD1 having the central light emission wavelength closer to
the short wavelength than the stipulated light emission wavelength
and the semiconductor light emitting element LD2 closer to the long
wavelength is used, the central wavelength of the synthetic laser
light when changing the light emission wavelengths and the light
emission amounts thereof is obtained through analysis, and the
central wavelength is stored in the wavelength conversion table.
Then, as described above, the light source control section 49
controls the light emission intensities of the semiconductor light
emitting elements LD1 and LD2 on the basis of the wavelength
conversion table so that the central wavelength of the synthetic
laser light is equal to a predetermined light emission wavelength.
Accordingly, even the semiconductor light emitting elements LD1 and
LD2 not considered as the standard products may be used as the
light emission sources of the blue laser light sources 45 and 47
which are required to supply illumination lights having stipulated
wavelengths with high precision to the endoscope front end portion
35, and the cost of the endoscope apparatus 100 may be reduced.
[0064] Even in the light source device 41 for performing white
illumination by exciting the fluorescent substance 57 using the
blue laser light to emit light therefrom, in the case where the
absorption spectrum of the fluorescent substance 57 is formed as a
steep profile in the blue wavelength bandwidth, the light emission
efficiency of the fluorescent substance 57 is increased or
decreased in accordance with a slight variation in the wavelength
of the blue laser light sources 45 and 47. As a result, even when
the fluorescent substance 57 is illuminated by the same light
emission intensity, the light emission amount of the fluorescent
substance 57 is decreased, which may cause a bluish-white
illumination. However, according to the endoscope apparatus 100
with such a configuration, since the central wavelength of the
synthetic laser light may be controlled with high precision to be
an arbitrary wavelength as a target, the light emission spectrum
illuminates uniform white light, thereby displaying the observation
image on the display unit 15 with satisfactory tone at all
times.
[0065] In addition, the light emission wavelengths of the
above-described semiconductor light emitting elements LD1 and LD2
may be measured at an appropriate timing, and the information of
the storage section 75 may be rewritten. FIG. 9 is a conceptual
block diagram of the endoscope apparatus 100 of the modified
example 1 in which the information of the storage section 75 may be
rewritten. In FIG. 9, since the same reference numerals are given
to the same components as those shown in FIG. 1, the description
thereof is omitted.
[0066] As shown in FIG. 9, in the endoscope apparatus 100 of the
modified example 1, reflection means 81 and 83 such as a beam
splitter or a galvanic mirror are disposed in the course of the
light path connecting the blue laser light sources 45 and 47 to the
combiner 51 as the multiplexer. The laser lights emitted from the
blue laser light sources 45 and 47 exit from the light path while
being reflected by the reflection means 81 and 83, and are output
to the connector 25C installed in the control device 13.
[0067] Then, the wavelengths of the laser lights of the blue laser
light sources 45 and 47 are measured by the wavelength measurement
device 85 connected to the connector 25C, and the measurement
result is written to the storage section 75 via the light source
control section 49. Accordingly, even in the case where there is a
variation in the characteristics of the semiconductor light
emitting elements LD1 and LD2, or the semiconductor light emitting
elements LD1 and LD2 are exchanged with another by maintenance and
the like after the shipment of the endoscope apparatus 100, it is
possible to supply the illumination light having an accurate
stipulated wavelength at all times, and to display an image having
a correct color on the display unit 15. In the application field of
the endoscope apparatus 100, it is easy to perform a periodic
calibration. The writing process to the storage section 75 may be
performed in a manufacture factory after transporting the endoscope
apparatus 100 to manufacturing factory, or may be performed in the
application field.
[0068] In addition, the configuration of the endoscope apparatus
100 may be modified into various forms. For example, the number of
the semiconductor light emitting elements LD used for the
multiplexing operation is not limited to two of the above-described
LD1 and LD2, but may be an arbitrary number. FIG. 10 is a block
diagram showing a configuration of a main part of the light source
device of the modified example 2, where one light source device 41
is provided with n number of light emitting elements LD1, LD2, LD3,
. . . , LDn, and the laser lights respectively emitted from the n
number of semiconductor light emitting elements LD1, LD2, LD3, . .
. , LDn are multiplexed by the combiner 51. When the laser lights
emitted from the plurality of semiconductor light emitting elements
LD1, LD2, Ld3, . . . , LDn are multiplexed, it is possible to allow
the spectral profile of the synthetic laser light to be close to
the smoother Gauss distribution profile compared with the case
where two semiconductor light emitting elements LD1 and LD2 are
used. At this time, it is desirable to use the combination of the
light sources having different light emission wavelengths
.lamda..sub.1 to .lamda..sub.n so that the adjustment bandwidth of
the wavelength of the multiplexed light becomes large.
[0069] FIG. 11 is a block diagram showing a configuration of a main
part of the light source device of the modified example 3, where
the light sources LD used for the multiplexing operation may be the
light sources having plural types of wavelength bandwidths. In the
modified example 3 shown in FIG. 11, one light source device 41 is
provided with the combination of two semiconductor light emitting
elements LD-A1 and LD-A2 having a stipulated wavelength of 445 nm
and another two semiconductor light emitting elements LD-B1 and
LD-B2 having a stipulated wavelength of 405 nm. When the laser
lights respectively emitted from these four semiconductor light
emitting elements LD-A1, LD-A2, LD-B1, and LD-B2 are multiplexed by
the combiner 51, the wavelength .lamda..sub.A averaged around the
wavelength of 445 nm and the wavelength .lamda..sub.B averaged
around the wavelength of 405 nm are formed.
[0070] In this case, when the lights emitted from the plurality of
semiconductor light emitting elements stipulated to have the same
wavelength are multiplexed, it is possible to absorb differences in
the wavelength caused by individual differences of each of the
semiconductor light emitting elements, and to arrange the
wavelengths of the illumination lights. For example, the standard
light emission wavelengths of the semiconductor light emitting
elements LD-A1 and LD-A2 are 445 nm, but in actual application, the
semiconductor light emitting elements have individual differences
due to differences in manufacturing. For this reason, the
semiconductor light emitting elements may emit lights having
wavelengths deviating from 445 nm by, for example, .+-.5 nm.
Accordingly, as shown in FIG. 11, the lights of the plurality of
semiconductor light emitting elements LD-A1 and LD-A2 are
multiplexed and used, and in the same way, the lights of the
plurality of semiconductor light emitting elements LD-B1 and LD-B2
are multiplexed and used, thereby averaging differences in the
wavelength of the semiconductor light emitting element. As a
result, the wavelengths of the multiplexed lights are 445 nm and
405 nm, and differences in the light emission wavelength and the
like caused by individual differences may be reduced compared with
the case where one laser light source is used.
[0071] Likewise, the present invention is not limited to the
above-described embodiment, but corrections and applications
thereof may be made by the person skilled in the art on the basis
of the description of the specification and the known technology,
and those are included in the scope required to be protected.
[0072] As described above, the present specification discloses the
following items.
[0073] (1) An endoscope apparatus including: an endoscope which
includes an illumination optical system having a fluorescent
substance; a light source unit which is connected to the endoscope,
includes a plurality of semiconductor light emitting elements
having different central light emission wavelengths, and supplies
light from the semiconductor light emitting elements to the
illumination optical system; a multiplexer means for multiplexing
the lights output from the plurality of semiconductor light
emitting elements; and a central wavelength converting means for
controlling a light emission amount ratio of the plurality of
semiconductor light emitting elements and converting the central
wavelength of the light multiplexed by the multiplexer means.
[0074] According to the endoscope apparatus, it is possible to
highly precisely maintain the wavelength of the light emitted from
the semiconductor light emitting element to be a stipulated
constant value, and to generate light of a stipulated wavelength
even in the single semiconductor light emitting element of which
the light emission wavelength is not included in the stipulated
wavelength range. Accordingly, it is possible to prevent
deterioration in the illumination light amount or imaging
sensitivity, and to reduce the cost of components of the endoscope
apparatus.
[0075] (2) The endoscope apparatus according to (1), wherein the
central wavelength converting means has a wavelength conversion
table in which the central wavelength of the light formed by
multiplexing the lights emitted from the plurality of semiconductor
light emitting elements is obtained on the basis of information of
the light emission amounts and the central light emission
wavelengths of the plurality of semiconductor light emitting
elements, and the light emission amount ratio of the semiconductor
light emitting elements is determined by referring to the
wavelength conversion table.
[0076] According to the endoscope apparatus, the wavelength
conversion table is created, and the light emission amount of each
of the semiconductor light emitting elements is controlled on the
basis of the wavelength conversion table. Accordingly, it is
possible to simply adjust the wavelength of the light emitted from
the semiconductor light emitting element at an arbitrary
timing.
[0077] (3) The endoscope apparatus according to (1), wherein a
plurality of the fluorescent substances is disposed at different
positions of an endoscope front end portion inserted into a test
object, and wherein the endoscope apparatus further includes a
demultiplexer means which demultiplexes the multiplexed light and
supplies the demultiplexed light to each of the plurality of
fluorescent substances.
[0078] According to the endoscope apparatus, the plurality of
fluorescent substances are disposed at the plurality of positions
of the endoscope front end portion, and the light demultiplexed by
the demultiplexer means is supplied to each of the fluorescent
substances. Accordingly, it is possible to illuminate the test
object with uniform illumination light without generating shadows
on the test object.
[0079] (4) The endoscope apparatus according to (1), further
including: an output light extracting means for individually
extracting the lights output from the plurality of semiconductor
light emitting elements in the course of an optical path; and a
wavelength measurement means for measuring the wavelength of each
of the lights extracted by the output light extracting means,
wherein the central wavelength converting means determines the
light emission amount ratio on the basis of the wavelength
measurement values of the lights emitted from the plurality of
semiconductor light emitting elements.
[0080] According to the endoscope apparatus, the wavelength of the
light emitted from each of the semiconductor light emitting
elements is measured, and the light emission amount ratio is
controlled on the basis of the wavelength measurement value.
Accordingly, it is possible to more accurately adjust the central
wavelength of the multiplexed light. Therefore, even in the case
where the semiconductor light emitting element is exchanged with
another by maintenance and the like, and the characteristics of the
semiconductor light emitting element are changed with time, it is
possible to more accurately adjust the central wavelength of the
multiplexed light.
[0081] (5) An illumination control method of an endoscope apparatus
including an endoscope which includes an illumination optical
system having a fluorescent substance; and a light source unit
which is connected to the endoscope, includes a plurality of
semiconductor light emitting elements having different central
light emission wavelengths, and supplies light from the
semiconductor light emitting elements to the illumination optical
system, the illumination control method including at least the
steps of: measuring the central light emission wavelength of each
of the semiconductor light emitting elements; obtaining a central
wavelength of light formed by multiplexing the lights output from
the plurality of semiconductor light emitting elements through
analysis in accordance with setting values of the central light
emission wavelength of each of the semiconductor light emitting
elements and a light emission amount of each of the semiconductor
light emitting elements, and registering the central wavelength in
a wavelength conversion table; determining the light emission
amount ratio of the semiconductor light emitting elements so that
the central wavelength of the multiplexed light is equal to a
target wavelength on the basis of the wavelength conversion table;
and driving the semiconductor light emitting elements in accordance
with the determined light emission amount ratio.
[0082] According to the illumination control method of the
endoscope apparatus, it is possible to highly precisely generate
laser light of a stipulated wavelength from not only a
semiconductor light emitting element having the light emission
wavelength included in the stipulated wavelength range, but also a
single semiconductor light emitting element having a light emission
wavelength not included in the stipulated wavelength range.
Accordingly, it is possible to prevent deterioration in the
illumination light amount or imaging sensitivity, and to reduce the
cost of components of the endoscope apparatus.
* * * * *